AirBnb, based on comments here it seems quite clear the majority of hosts do not agree with your position of mandating "Under 2 is Free".
These are our business. We decide our rates and tariff policies. You are forcing our hand to take measures to navigate around this issue. Your software should support us by allowing us to stipulate in a variable field, "infants free under X" age, as many other booking engines do.
You are losing commission revenue because of this limitation, through both potentially increased tariffs, and the loss of booking requests all together.
Please consider this 'enhancement' as a matter of urgency in your future software releases.